Well if you overclock using your Bus it will overclock the HT. Plus some boards will have a higher multi for the HT in the bios. Not for sure if this one does or not, would have to reboot and see, never really looked for it.
The Phenom II HT seems to run pretty stable over 2000/4000. The thing about it is even overclocking your not bottlenecking the HT anyway so there is little or no performance gain.
If you want to use the bus to overclock and having your HT, memory, northbridge all overclocked might get you alittle bit all together compared to just using your CPU multi. and leaving everything else stock.